Half-empty or half-full? It's a dam good question

ELFIN FOREST -- Rain or shine, the county's newest lake
continues to rise -- 1 gallon at a time. Olivenhain Reservoir has
come a long way since August, when the first cascade of imported
water spilled from a 54-inch pipe onto powdery ground.

The reservoir now is more than half-full, officials said last
week; by June, 8 billion gallons should lap at its man-made
brim.

The water's surface already spreads across a vast saddle within
the scrubby hills between Encinitas and Escondido. When full, the
lake should cover 200 acres.

At its western edge, the man-made lake leans against a
318-foot-tall dam. Three hundred workers spent three years rolling
and compacting the dam's 159 2-foot-tall steps, which are layered
like an enormous, petrified cake.

That cake assumed a new hue this fall: Workers coated its gray
surface with a magnesium and iron-oxide compound so the dam would
look brown like the rocks in surrounding hills.

On Wednesday, Olivenhain Municipal Water District General
Manager David McCollom assessed the ever-growing lake, which looked
smooth and reflective like steel. He figured 100 vertical feet
remain between the surface and the dam's high-water mark at 1,080
feet above sea level.

While a full lake will represent a milestone, it does not signal
a finished project.

Part of the whole

Olivenhain Reservoir is but one of 17 components of San Diego
County Water Authority's Emergency Storage Project, an $827 million
undertaking to create water reserves should drought, earthquakes or
other calamities isolate the county from faraway sources.

The authority represents 23 member agencies and serves as the
region's importer and wholesale supplier of water from the Colorado
River and Northern California.

Two aqueducts deliver 90 percent of the water consumed in the
county. One of them, which officials refer to as the Second San
Diego Aqueduct, furnishes the water to fill Olivenhain
Reservoir.

The Emergency Storage Project will connect three reservoirs --
Olivenhain Reservoir, San Vicente Reservoir and Lake Hodges -- to
the two aqueducts and, in effect, to each other.

Gravity alone carries water through the south-flowing aqueducts.
That is why the storage project includes a network of connections
and pumps to move water as far north as Fallbrook and to other
areas that need it.

One of those linkages sits smack in the center of North County
and will bridge Olivenhain Reservoir to parched and pathetic Lake
Hodges. The lake is contained within San Diego's northernmost city
limits near Escondido. Del Dios Highway and the unincorporated
community of Del Dios overlook the western shoreline.

A growing problem

The Water Authority plans to bore a 1.5-mile tunnel to connect
Olivenhain Reservoir to Lake Hodges, but faces a growing
problem.

A forest is proliferating atop some 300 acres of Hodges' dry
lake bed. For water officials, the willows and brush present a
two-pronged headache.

All that plant material, when flooded, could contaminate the
drinking water.

What's more, the vegetation could be off-limits for removal
because it provides a home for endangered plants and birds.

Two local districts serving Encinitas -- Solana Beach and Rancho
Santa Fe -- are clearing some non-native plants from the lake bed
at the points nearest to where the lake would rise after a
rainfall, said Mary Putnam, a water resources specialist for the
authority.

San Dieguito Water District and Santa Fe Irrigation District
both purchase Lake Hodges water from the city of San Diego. While
workers employed by the two agencies prepare Lake Hodges for rain
-- should rain ever come -- a thorough cleaning of the lake bed
would not happen until shortly before the authority fills it in
2008, she said.

The authority has secured state and federal permits to clean
Lake Hodges, a collection point for San Diego County's largest
watershed.

The San Dieguito River watershed is a drainage area that
encompasses 346 square miles between Volcan Mountain and the ocean
at Del Mar.

While the city of San Diego owns all of Lake Hodges and sells
its water, Olivenhain Municipal Water District owns one-sixth of
Olivenhain Reservoir, and the authority controls the remainder.

When the time comes to fill Lake Hodges, state and federal
officials will determine what the Water Authority must do to
compensate for the environmental disruption caused by the lake bed
cleaning, she said.

"There's a lot of trees out there," Putnam said.

Of tunnels and pumps

When filled, Lake Hodges again will follow a course carved by
sinuous San Dieguito River from Del Dios Highway to points east of
Interstate 15.

Depending on the lake level at the time, filling it will take
about three months.

A 13-foot-diameter tunnel is planned to travel through layer
after layer of granite at depths of up to 600 feet to link Lake
Hodges to Olivenhain Reservoir, said Tim Smith, a senior civil
engineer for the Water Authority.

Portions of the tunnel would be so solid that a steel lining
would be unnecessary, he said.

The $100 million tunneling project is scheduled to begin in
2006.

The project includes a pump at Lake Hodges that can send water
right back to Olivenhain Reservoir should Hodges begin to spill. It
also includes turbines to harness the energy and make electricity
from the water as it falls 700 vertical feet from Olivenhain
Reservoir to Lake Hodges below.

The tunnel will connect to Lake Hodges on its western shoreline
near Del Dios.

Crews will work uphill to bore the tunnel, for which a final
design remains incomplete. Also undetermined is whether contractors
will use modern boring techniques or blasting and drilling, Smith
said.

"We're allowing contractors to bid either way," he said, "to get
the best price."

For the time being, heavy construction at Olivenhain Reservoir
is finished, giving water district manager McCollom time to reflect
upon the ever-filling lake and the billions of gallons it
holds.

The county's first major dam to open in 50 years and the largest
dam of its kind in the country gives McCollom plenty of good
feelings, but one seems to rise above all others.